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Please Explain Client Mode, AP Mode, WDS

Discussion in 'Sveasoft Firmware' started by twodaend, Aug 12, 2005.

  1. twodaend

    twodaend LI Guru Member

    I have a WRT54G with the Linksys firmware and everything is running fine. A friend just gave me his WRT54G so I decided to try putting the Alchemy 1.0 firmware on. It has a lot more features the the stock one. Both WRT54G's are v3.

    I was wondering if someone could give a detail explation and/or example of what Client Mode, AP Mode and WDS are. I sort think I know what AP mode and WDS are, but really not sure what client mode is. Here is what I think:

    Client Mode
    1) Not sure

    AP Mode
    1) WRT54G will act as an access point only for wireless clients.
    2) Not sure if 4 LAN ports will work.
    3) Not sure if connection is done wired or wireless back to main router.

    WDS
    1) Connecting 2 or more WRT54G wireless
    2) I believe all 4 LAN ports will work on each WRT54G

    Please correct me or add more detail's/examples to each as this is just my best guess and I don't totally understand any of them.

    My Current Setup
    [​IMG]

    Will I benefit from either of these setups, possibly by replacing my WET54GS5?

    Thanks for all the help
  2. 4Access

    4Access Network Guru Member

    In client mode the router functions as a wireless client. It will associate with another access point. You can plug computers into the LAN ports but wireless clients can NOT connect to it. The router would function somewhat similar to the WET54GS5, WET54G, WET11, WUSB54G, etc. etc.

    Note that all the current stable firmware available for the WRT requires that when the WRT is in Client Mode it must route between the LAN ports & the wireless network it is connected to. This means that the clients on the LAN ports of the WRT must use a different subnet than the wireless network uses. For example:

    [MainRouter] ~~~~ 1. ~~~~ [Client Mode WRT] ---- 2. ---- [PC's etc.]

    1. MainRouter Wireless Network =192.168.1.x
    2. Client Mode Wired Network =192.168.0.x

    The next generation of custom firmware for the WRT (DD-WRT v23 & Sveasoft's Talisman, both currently in beta) are going to support a bridged client mode where the clients connected to the LAN ports on a WRT can use the same subnet as the wireless network!
    :thumbup: In fact you can even test the functionality in DD-WRT now. See here (remember this is a pre-beta release so don't complain about the bugs!)


    When in AP mode the router functions as an access point. Wireless clients can connect to the router. The LAN ports can also be used. (In fact, in AP mode you can think of the antenna's as just another LAN port.)
    When in AP mode, to connect to another router you must either run a cable between the routers or enable WDS.

    WDS = Wireless Distribution System. Think of this as wireless repeater mode. In this mode the router can communicate wirelessly with another router that supports WDS. Not only can the LAN ports be used but wireless clients can connect to the router as well. The reason it is considered a repeater mode is because the signals from wireless clients connected to one router will be repeated to the other router. (Traffic from the clients connected on the LAN ports will also be repeated to the other router as well.)

    The benefit you would get by switching your WET54GS5 with another WRT is that you could use WDS and then the WRT could extend the wireless range of your laptop as well as connect your PS2 & Media PC to your network.
  3. twodaend

    twodaend LI Guru Member

    Thanks for the info. I have the 2 WRT54G working in WDS mode and it seems to be working fine. The media PC streams are smoother and the PS2 can go online without lag. I thought WDS cutting the bandwith in half I may have a problem, but then I read that the transmitt power on the WRT54G is strong than the WET54GS5 so they may explain why I'm getting good throughput.

    Thanks again for your detailed explaination.
  4. 4Access

    4Access Network Guru Member

    Regarding the WDS throughput issue:

    Firstly 802.11g equipment is rated at 54Mbps. This means that the radio in an 802.11g NIC or Router can transmit at 54Mbps. (Due to the overhead associated with wireless protocols you won't get more than 20-24Mbps of useable throughput under optimal conditions though.)

    Additionally, and of importance to this conversation, wifi radios are half-duplex. They can transmit & receive but they can only do one at a time. (Similar to a walkie talkie or CB radio etc.)

    It is this half-duplex characteristic of repeaters which cuts throughput in half.
    Whenever a wifi signal is repeated the repeating device must wait to receive the signal before it can transmit (repeat) it. The repeater can't both receive the signal and repeat it simultaneously.

    One of the primary uses for WDS is wireless repeating which is where all the talk of "cutting your bandwidth in half" comes from.

    Some illustrations may help. First, a "normal" (non WDS) connection:

    In the illustration below you get your full throughput potential because the router can receive the wireless signal and simultaneously send it out the wired port.

    Wireless Client ~~~ [Router] --- Wired Client

    But in the following example your throughput is cut in half because the 1st router cannot receive the signal and repeat it to the 2nd router at the same time due to the half-duplex nature of its wifi radio:

    Wireless Client ~~ [Router] ~~ WDS ~~ [Router] -- Wired Client

    In the illustation above the 1st router must wait until it has received the message before it can resend it to the 2nd router. (The 2nd router can pass the traffic along to the wired client as it receives it though.)

    What this shows is that for every additional wireless "hop" the throughput is cut in half. In the following example your throughput would be cut in half 3 times!

    Wireless Client ~~ [Router] ~~ WDS ~~ [Router] ~~ Wireless Client

    Above, the data must be transmitted to the 1st router, repeated to the 2nd router, and finally repeated to the receiving wireless client.

    With that said, simply because you are using WDS it does not mean that your throughput is automatically cut in half. For example:

    Wired Client -- [Router] ~~ WDS ~~ [Router] -- Wired Client

    In the example above two wired clients are communicating over a WDS connection, but since there is only one wireless "hop" you can achieve the full throughput potential of the wireless connection. (The 1st router can transmit the data wirelessly as it receives it from the wired client. And on the other end, the 2nd router can send the data to the wired client as it receives the wireless signal.)

    Make sense?

    Here's another one that most people don't realize... What is going to happen in the example below:

    Wireless Client ~~~ [Router] ~~~ Wireless Client

    We've got 2 wireless hops right? One from the 1st wireless client to the router and then another one from the router to the 2nd wireless client! ... No WDS yet the throughput is cut in half because both clients are wireless and the router must "repeat" the signal from the 1st client to the 2nd!!! :shock:

    Because of this, your throughput would be faster if you configured an Ad Hoc network when you need to transfer a lot of data between two wireless clients because:

    Wireless Client ~~~ Ad hoc ~~~ Wireless Client

    There is only one wireless "hop" between the clients.



    BTW I don't mean to lecture at you I just see a lot of confusion on the WDS throughput issue and I intend to use this post as a general reference. ;)
  5. twodaend

    twodaend LI Guru Member

    Excellent post. With your examples, WDS makes a bit more sense now and I understand what is going on better. Thanks for all the info and I will be refering back to this post just in case I get confused on something.

    Thanks for all the time and effort you put into explaining WDS.
  6. niceboy

    niceboy LI Guru Member

    Hello

    I'm sure that it right her!

    I would know wether the Freya Firmware on the WAP54G can communicate with other Producer in the client-mode? Example: Linksys WAP54G Client --> Lancom or Netgear AP

    thx
  7. vincentfox

    vincentfox Network Guru Member

    I would expand a bit on the "client" modes.

    I don't think it is adequately mentioned, that classic AP-client mode only supports a single LAN port in use. You are essentially treating the WRT like one great big USB WiFi adapter. It does have advantages though, you can only run USB short distances. If you have a desktop PC in some dungeon though you can run ethernet up to 100 meters up to some point where the WRT can pick up good signal.

    There are also other good uses for this. You can use an AP-client unit outside the house to pick up WISP service. Then run ethernet from it, to the WAN port of a router inside the house. Now you have an internal network that can be NAT'ed and have it's own LAN and it's own WiFi, all based off a single connection and IP from the WISP.

    There are some firmware such as DD-WRT that support directly client-bridged or client-routed mode. These allow you to have many PC attached on the LAN ports. I do not know if Talisman has this yet, I think it didn't work in 1.0.5.
  8. 4Access

    4Access Network Guru Member

    Just wanted to reemphasize that you can connect more than one client to the LAN ports with DD-WRT. I don't keep up with Sveasoft much anymore but my understanding is that it worked in Alchemy so I don't know why it wouldn't in Talisman...
  9. StoneRoses

    StoneRoses LI Guru Member

    Sorry for bringing up old thread but I realize that there might be some misconception about the througput and the number of wireless hops.

    Don't get me wrong, I think 4Access' explanation is mostly accrurate except this part

    In my view, in this case (3 hops), the throughput should be 1/3 of 1-hop transmission not 1/4 or 1/8 that 4Access mention.

    If I'm wrong, please correct me.

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